Field of the Invention
The present technology relates to one or more of the diagnosis, treatment and amelioration of respiratory disorders. In particular, the present technology relates to medical devices, and their use for treating respiratory disorders.
Description of the Related Art
Respiratory Disorders
The respiratory system of the body facilitates gas exchange. The nose and mouth form the entrance to the airways of a patient.
The airways include a series of branching tubes, which become narrower, shorter and more numerous as they penetrate deeper into the lung. The prime function of the lung is gas exchange, allowing oxygen to move from the air into the venous blood and carbon dioxide to move out. The trachea divides into right and left main bronchi, which further divide eventually into terminal bronchioles. The bronchi make up the conducting airways, and do not take part in gas exchange. Further divisions of the airways lead to the respiratory bronchioles, and eventually to the alveoli. The alveolated region of the lung is where the gas exchange takes place, and is referred to as the respiratory zone. See West, Respiratory Physiology—the Essentials.
A range of respiratory disorders exist.
Cheyne-Stokes Respiration (CSR) is a disorder of a patient's respiratory controller in which there are rhythmic alternating periods of waxing and waning ventilation, causing repetitive de-oxygenation and re-oxygenation of the arterial blood. It is possible that CSR is harmful because of the repetitive hypoxia. In some patients CSR is associated with repetitive arousal from sleep, which causes severe sleep disruption, increased sympathetic activity, and increased afterload. See U.S. Pat. No. 6,532,959 (Berthon-Jones).
Obesity Hyperventilation Syndrome (OHS) is defined as the combination of severe obesity and awake chronic hypercapnia, in the absence of other known causes for hypoventilation. Symptoms include dyspnea, morning headache and excessive daytime sleepiness.
Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a group of lower airway diseases that have certain characteristics in common. These include increased resistance to air movement, extended expiratory phase of respiration, and loss of the normal elasticity of the lung. Examples of COPD are emphysema and chronic bronchitis. COPD is caused by chronic tobacco smoking (primary risk factor), occupational exposures, air pollution and genetic factors. Symptoms include: dyspnea on exertion, chronic cough and sputum production.
Neuromuscular Disease (NMD) is a broad term that encompasses many diseases and ailments that impair the functioning of the muscles either directly via intrinsic muscle pathology, or indirectly via nerve pathology. Some NMD patients are characterised by progressive muscular impairment leading to loss of ambulation, being wheelchair-bound, swallowing difficulties, respiratory muscle weakness and, eventually, death from respiratory failure. Neuromuscular disorders can be divided into rapidly progressive and slowly progressive: (i) Rapidly progressive disorders: Characterised by muscle impairment that worsens over months and results in death within a few years (e.g. Amyotrophic lateral sclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers); (ii) Variable or slowly progressive disorders: Characterised by muscle impairment that worsens over years and only mildly reduces life expectancy (e.g. Limb girdle, Facioscapulohumeral and Myotonic muscular dystrophy). Symptoms of respiratory failure in NMD include: increasing generalised weakness, dysphagia, dyspnea on exertion and at rest, fatigue, sleepiness, morning headache, and difficulties with concentration and mood changes.
Chest wall disorders are a group of thoracic deformities that result in inefficient coupling between the respiratory muscles and the thoracic cage. The disorders are usually characterised by a restrictive defect and share the potential of long term hypercapnic respiratory failure. Scoliosis and/or kyphoscoliosis may cause severe respiratory failure. Symptoms of respiratory failure include: dyspnea on exertion, peripheral oedema, orthopnea, repeated chest infections, morning headaches, fatigue, poor sleep quality and loss of appetite.
Therapy
Ventilation has been used to treat CSR, OHS, COPD, MD and Chest Wall disorders.
PAP Devices
The air at positive pressure for ventilation is typically supplied to the airway of a patient by a PAP device or ventilator such as a motor-driven blower. The outlet of the blower is connected via a flexible delivery conduit to the airway of the patient.
Tracheostomy
Tracheostomy is a surgical procedure in which an incision on the anterior of the neck is made in order to open an airway into the trachea of a patient. Through the resulting opening a tracheostomy tube is inserted into the patient's trachea in order to allow him to breathe without the use of his upper airways.
A PAP device or ventilator used with such a tracheostomy tube can assist a patient by providing him with pressurised air or other breathable gas via the tube when the patient inhales, and by allowing exhaled air to be evacuated via the tube when the patient exhales.
One known ventilator suitable for tracheostomy patients is the Elisée, manufactured by ResMed.
Speech Difficulty
While connected to a valved ventilator, e.g. under uncuffed tracheostomy, the patient may attempt to speak. The normal operation of the ventilator will impair the quality of that speech by allowing the exhaled air to pass through the tracheostomy tube instead of through the upper airway, where the vocal cords are located.
Air being exhaled via a tracheostomy tube can impair speech from a patient under ventilation as the exhaled air is diverted from flowing through the patient's upper airway and along his vocal cords. To enable speech, a pressure below the vocal cords (between the lung and the vocal cords) above a minimum value of approximately 3 hPa is normally required. This is typically done in a non-tracheostomised person by contracting the vocal cords while there is air inside the lungs (after an inhalation). The pressure will then be the result of the normal exhalation of air through the vocal cords and then the mouth. On a tracheostomised patient, however, most of the exhaled air is not routed through the upper airway as the tracheostomy tube is located below the vocal cords, and it is easier for the air to pass through the exhalation valve of the breathing assistance system than through the upper airway.
According to an existing solution, the usual value of PEEP (Positive End-Expiratory Pressure) is increased by the PAP device so that the majority of exhaled air is redirected along the upper airway. According to another solution, a non-return valve, such as a Passy-Muir valve, is positioned along the conduit so that the only possible route for the exhaled air is via the upper airway.
French patent application no. FR 2945217 relates to a breathing assistance device for a tracheostomy patient that is said to facilitate breathing and speech of the patient. The assembly has an expiration circuit with an outlet opening for passage of the air exhaled by the patient, and a valve for opening/closing the outlet opening. When the patient inhales, the valve closes the outlet opening and when the patient exhales the valve opens the outlet opening. The device is also provided with means for positive control to be actuated by the patient for selectively moving the valve into the closed position when the patient exhales, so that the exhalation is via the upper airway, i.e., when he wishes to speak, or to a state where exhalation is done via the tracheostomy tube, i.e., when he does not wish to speak.
Most of the known solutions are permanent, i.e. they are kept constant throughout the therapy. Although allowing the patient to speak, they run counter to the whole purpose of tracheostomy. Only the device according to FR 2945217 is not permanent in that it provides a patient button to be activated by the patient. This activation thus requests a conscious act from the patient and also an ability to do so. This is problematic since the patient category that would benefit from such a feature (such as neuromuscular patients) often has a very limited ability to do so.